Isothermal section of the Er-Mn-Sn system at 670 K

Abstract

Interaction between the components in the Er - Mn - Sn ternary system was studied at 670 K over the whole concentration range using methods of X-ray diffractometry, metallography and electron microprobe analysis. The alloys for investigation were prepared by direct arc melting the stoichiometric amounts of the constituent elements under high purity Ti-gettered argon atmosphere on a water-cooled copper hearth. The arc-melted ingots were then annealed at 670 K in evacuated quartz glass tubes for 720 hours and subsequently cold water quenched. The synthesized and annealed samples are stable in atmospheric conditions. For the characterization of the annealed samples X-ray powder diffraction on DRON-2.0m diffractometer with Fe K α radiation was performed. The chemical and phase compositions of the obtained samples were examined by Scanning Electron Microscopy (SEM) (REMMA-102-02 electron microscope). A formation of the all binaries in the Er-Sn, Er-Mn and Mn-Sn systems which delimit the studied Er-Mn–Sn was confirmed. According to EPMA data the homogeneity range of Mn 2 Snbinary is limited by the Mn 67,81 Sn 32,19 and Mn 63,87 Sn 36,13 compositions. At the temperature of investigation phase relations in the Er-Mn-Sn system are characterized by existence of two ternary compounds ErMn 6 Sn 6 (MgFe 6 Ge 6 structure type, space group P 6/ mmm , a =0.55157(7) nm, с =0.90051(1) nm) and Er 4 Mn 4 Sn 7 (Zr 4 Co 4 Ge 7 structure type, space group I 4/ mmm , a =1.4869(3) nm, c =0.5951(1) nm). During investigation of Er-Mn-Sn system the existence of interstitial solid solution ErMn 0- х Sn 2 based on the ErSn 2 binary (ZrSi 2 -type) was observed. The solubility of Mn atoms was found to be up to 5 at. % at 670 K. The lattice parameters change from а = 0.4369(9), b = 1.16138(8), с = 0.4273(9) нм nm (for ErSn 2 compound) to а = 0.4370(8), b = 1.6141(9), с = 0.4287(4) nm for Er 32 Mn 5 Sn 63 sample. Limited composition of the solid solution was confirmed by results of EDX analysis (Er 32.44 Mn 4.88 Sn 62.68 ). Solubility of the third component in other binary compounds is less than 1-2 at. %. Analysis of the Er-Mn-Sn system and studied early {Y, Ce, Nd, Gd, Dy}-Mn-Sn showed that the ternary R-Mn-Sn systems are characterized by small number of the intermediate phases. Stannides with CeNiSi 2 and Gd 3 Cu 4 Ge 4 structure types are formed only in the systems with rare earths of Cerium group. R-Mn-Sn systems where R is a rare earth element of Yttrium group are characterized by formation of the ternary compounds with Zr 4 Co 4 Ge 7 -type and MgFe 6 Ge 6 structure types, which are realized in the studied Er-Mn-Sn system. Keywords: intermetallics, ternary system, phase equilibria.